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Getting Started With WordPress Block Development

Getting Started With WordPress Block Development

In this article, I intend to help you get started with WordPress block development in a way that follows the current methodology. So, yes, things could very well change after this is published. But I’m going to try and focus on it in a way that hopefully captures the essence of block development, because even though the tools might evolve over time, the core ideas are likely to remain the same.

Apart from these core blocks, we can create custom blocks too. That is what WordPress block development is about (there’s also filtering core blocks to modify their functionality, but you likely won’t be needing that just yet).

Before we dive into creating blocks, we must first get some sense of how blocks work internally. That will definitely save us a ton of frustration later on.

The way I like to think about a block is rather abstract: to me, a block is an entity, with some properties (called attributes), that represents some content. I know this sounds pretty vague, but stay with me. A block basically manifests itself in two ways: as a graphical interface in the block editor or as a chunk of data in the database.

When you open up the WordPress Block Editor and insert a block, say a Pullquote block, you get a nice interface. You can click into that interface and edit the quoted text. The Settings panel to the right side of the Block Editor UI provides options for adjusting the text and setting the block’s appearance.

When you are done creating your fancy pullquote and hit Publish, the entire post gets stored in the database in the wp_posts table. This isn’t anything new because of Gutenberg. That’s how things have always worked — WordPress stores post content in a designated table in the database. But what’s new is that a representation of the Pullquote block is part of the content that gets stored in post_content field of the wp_posts table.

What does this representation look like? Have a look:

Looks like plain HTML, right?! This, in technical lingo, is the “serialized” block. Notice the JSON data in the HTML comment, "textAlign": "right". That’s an attribute — a property associated with the block.

Let’s say that you close the Block Editor, and then some time later, open it again. The content from the relevant post_content field is retrieved by the Block Editor. The editor then parses the retrieved content, and wherever it encounters this:

…it says out loud to itself:

OK, that seems like a Pullquote block to me. Hmm.. it’s got an attribute too… I do have a JavaScript file that tells me how to construct the graphical interface for a Pullquote block in the editor from its attributes. I should do that now to render this block in all its glory.

As a block developer, your job is to:

One thing to note is that all of this conversion from serialized data to graphical interface — and vice versa — takes place only in the Block Editor. On the front end, the content is displayed exactly the way it is stored. Therefore, in a sense, blocks are a fancy way of putting data in the database.

Hopefully, this gives you some clarity as to how a block works.

Blocks are just plugins. Well, technically, you can put blocks in themes and you can put multiple blocks in a plugin. But, more often than not, if you want to make a block, you’re going to be making a plugin. So, if you’ve ever created a WordPress plugin, then you’re already part-way there to having a handle on making a WordPress block.

But let’s assume for a moment that you’ve never set up a WordPress plugin, let alone a block. Where do you even start?

We have covered what blocks are. Let’s start setting things up to make one.

I personally go this route when setting up my own blocks, but humor me for a moment because I want to cut through the opinionated stuff it introduces and focus just on the required bits for the sake of understanding the baseline development environment.

These are the files I’d like to call out specifically:

In addition to these files, there’s also the src directory, which is supposed to contain the source code of our block.

Having these files and the src directory is all you need to get started. Out of that group, notice that we technically only need one file (plugin.php) to make the plugin. The rest either provide information or are used to manage the development environment.

The aforementioned @wordpress/create-block package scaffolds these files (and more) for us. You can think of it as an automation tool instead of a necessity. Regardless, it does make the job easier, so you can take the liberty of scaffolding a block with it by running:

Assuming you have the three files mentioned in the previous section ready, it’s time to install the dependencies. First, we need to specify the dependencies we will need. We do that by editing the package.json. While using the @wordpress/create-block utility, the following is generated for us (comments added; JSON does not support comments, so remove the comments if you’re copying the code):

The @wordpress/scripts package is the main dependency here. As you can see, it’s a devDependency meaning that it aids in development. How so? It exposes the wp-scripts binary that we can use to compile our code, from the src directory to the build directory, among other things.

You don’t actually need to install these packages, even if you want to use them. This is because these @wordpress dependencies aren’t bundled with your block code. Instead, any import statements referencing code from utility packages — like @wordpress/components — are used to construct an “assets” file, during compilation. Moreover, these import statements are converted to statements mapping the imports to properties of a global object. For example, import { __ } from "@wordpress/i18n" is converted to a minified version of const __ = window.wp.i18n.__. (window.wp.i18n being an object that is guaranteed to be available in the global scope, once the corresponding i18n package file is enqueued).

During block registration in the plugin file, the “assets” file is implicitly used to tell WordPress the package dependencies for the block. These dependencies are automatically enqueued. All of this is taken care of behind the scenes, granted you are using the scripts package. That being said, you can still choose to locally install dependencies for code completion and parameter info in your package.json file:

Now that package.json is set up, we should be able to install all those dependencies by navigating to the project folder in the command line and running npm install.

If you’re coming from classic WordPress plugin development, then you probably know that all plugins have a block of information in the main plugin file that helps WordPress recognize the plugin and display information about it on the Plugins screen of the WordPress admin.

Here’s what @wordpress/create-block generated for me in for a plugin creatively called “Hello World”:

That’s in the main plugin file, which you can call whatever you’d like. You might call it something generic like index.php or plugin.php. The create-block package automatically calls it whatever you provide as the project name when installing it. Since I called this example “Block Example”, the package gave us a block-example.php file with all this stuff.

You’re going to want to change some of the details, like making yourself the author and whatnot. And not all of that is necessary. If I was rolling this from “scratch”, then it might look something closer to this:

We’ve already looked at the required files for our block. But if you’re using @wordpress/create-block, you will see a bunch of other files in the project folder.

Here’s what’s in there at the moment:

Phew, that’s a lot! Let’s call out the new stuff:

I want to dig into the src directory with you but will focus first on just one file in it: block.json. If you’ve used create-block , it’s already there for you; if not, go ahead and create it. WordPress is leaning in hard to make this the standard, canonical way to register a block by providing metadata that provides WordPress context to both recognize the block and render it in the Block Editor.

Here’s what @wordpress/create-block generated for me:

One last thing before we hit actual code, and that’s to register the plugin. We just set up all that metadata and we need a way for WordPress to consume it. That way, WordPress knows where to find all the plugin assets so they can be enqueued for use in the Block Editor.

Registering the block is a two-fold process. We need to register it both in PHP and in JavaScript. For the PHP side, open up the main plugin file (block-example.php in this case) and add the following right after the plugin header:

This is what the create-block utility generated for me, so that’s why the function is named the way it is. We can use a different name. The key, again, is avoiding conflicts with other plugins, so it’s a good idea to use your namespace here to make it as unique as possible:

Why are we pointing to the build directory if the block.json with all the block metadata is in src? That’s because our code still needs to be compiled. The scripts package processes the code from files in the src directory and places the compiled files used in production in the build directory, while also copying the block.json file in the process.

Alright, let’s move over to the JavaScript side of registering the block. Open up src/index.js and make sure it looks like this:

We’re getting into React and JSX land! This tells WordPress to:

What’s up with the edit and save functions? One of the nuances of WordPress block development is differentiating the “back end” from the “front end” and these functions are used to render the block’s content in those contexts, where edit handles back-end rendering and save writes the content from the Block Editor to the database for rendering the content on the front end of the site.

We can do some quick work to see our block working in the Block Editor and rendered on the front end. Let’s open index.js again and use the edit and save functions to return some basic content that illustrates how they work:

This is basically a stripped-down version of the same code we had before, only we’re pointing directly to the metadata in block.json to fetch the block name, and left out the Edit and Save components since we’re running the functions directly from here.

We can compile this by running npm run build in the command line. After that, we have access to a block called “Block Example” in the Block Editor:

If we drop the block into the content area, we get the message we return from the edit function:

If we save and publish the post, we should get the message we return from the save function when viewing it on the front end:

Looks like everything is hooked up! We can revert back to what we had in index.js before the test now that we’ve confirmed things are working:

Notice that the edit and save functions are tied to two existing files in the src directory that @wordpress/create-block generated for us and includes all the additional imports we need in each file. More importantly, though, those files establish the Edit and Save components that contain the block’s markup.

This creates a Save component and we’re going to use pretty much the same thing as src/edit.js with slightly different text:

Again, we get a nice class we can use in our CSS:

We just covered how to use block props to create classes. You’re reading this article on a site all about CSS, so I feel like I’d be missing something if we didn’t specifically address how to write block styles.

If you take a look at the block.json in the src directory you’ll find two fields related to styles:

Recall that the @wordpress/scripts package copies the block.json file when it processes the code in the /src directory and places compiled assets in the /build directory. It is the build/block.json file that is used to register the block. That means any path that we provide in src/block.json should be written relative to build/block.json.

We could drop a couple of CSS files in the build directory, reference the paths in src/block.json, run the build, and call it a day. But that doesn’t leverage the full might of the @wordpress/scripts compilation process, which is capable of compiling Sass into CSS. Instead, we place our style files in the src directory and import them in JavaScript.

While doing that, we need to be mindful of how @wordpress/scripts processes styles:

In fact, when you spin up your initial block with @wordpress/create-block, you get a nice head start with SCSS files you can use to hit the ground running:

Let’s now see this approach in action by writing a little Sass that we’ll compile into the CSS for our block. Even though the examples aren’t going to be very Sass-y, I’m still writing them to the SCSS files to demonstrate the compilation process.

OK, let’s start with styles that are applied to both the front and back end. First, we need to create src/style.scss (it’s already there if you’re using @wordpress/create-block) and make sure we import it, which we can do in index.js:

Open up src/style.scss and drop a few basic styles in there using the class that was generated for us from the block props:

That’s it for now! When we run the build, this gets compiled into build/style.css and is referenced by both the Block Editor and the front end.

You might need to write styles that are specific to the Block Editor. For that, create src/editor.scss (again, @wordpress/create-block does this for you) and drop some styles in there:

Then import it in edit.js, which is the file that contains our Edit component (we can import it anywhere we want, but since these styles are for the editor, it’s more logical to import the component here):

Now when we run npm run build, the styles are applied to the block in both contexts:

We imported the styling files in the edit.js and index.js, but recall that the compilation step generates two CSS files for us in the build directory: index.css and style-index.css respectively. We need to reference these generated files in the block metadata.

Let’s add a couple of statements to the block.json metadata:

Run npm run build once again, install and activate the plugin on your WordPress site, and you’re ready to use it!

You can use npm run start to run your build in watch mode, automatically compiling your code every time you make a change in your code and save.

Actual blocks make use of the Block Editor’s Settings sidebar and other features WordPress provides to create rich user experiences. Moreover, the fact that there’s essentially two versions of our block — edit and save — you also need to give thought to how you organize your code to avoid code duplication.

But hopefully this helps de-mystify the general process for creating WordPress blocks. This is truly a new era in WordPress development. It’s tough to learn new ways of doing things, but I’m looking forward to seeing how it evolves. Tools like @wordpress/create-block help, but even then it’s nice to know exactly what it’s doing and why.

Are the things we covered here going to change? Most likely! But at least you have a baseline to work from as we keep watching WordPress blocks mature, including best practices for making them.

Again, my goal here is to map out an efficient path for getting into block development in this season where things are evolving quickly and WordPress documentation is having a little hard time catching up. Here are some resources I used to pull this together:


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